Corrosion inhibited lubricant composition



25,88,376 Patented Oct. 1, 1957 CURRQSIQN ITED LUBRICANT COOSITION Warren Lowe, Berkeley, Calif, assignor to California Research Corporation, San Francisco, Calif., a corpora= tion of Delaware No Drawing. Application December 29,

Serial No. 556,084

8 Claims. (Cl. 252-33.4)

This invention relates to a novel corrosion inhibited lubricant composition. More particularly, the invention is concerned with a new and unusually effective lubrieating oil composition having improved corrosion inhibiting properties.

Lubricating oils generally have a tendency to become Modern internal combustion engines in particular are operated under conditions which involve increased temperature changes, higher speeds and reduced clearances, all of which conditions aggravate the formation of corrosive decomposition products.

Unfortunately, activity of the and it is necessary to find inhibitors in combination with them.

Furthermore, many of the most effective corrosion inmetal-containing bearings which are subject to attack by active sulfur. These types of bearings, although once not so widely used and therefore considered to constitute only a minor problem, are being increasingly employed today. Particularly in certain important classes of internal combustion engines, as, for

containing bearings are more and more common, and the problem of providing proper lubrication for them from the standpoint of low corrosivity and improved lubricity is one of major importance.

A superior new corrosion inhibited lubricant composition has now been found comprising a major portion of an oil of lubricating viscosity corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit cor: rosion, of p-Xylylenediamine.

The novel lubricant composition according to the invention is characterized by remarkable corrosion inhibiting properties for metal surfaces and alloy bearings over extended periods of operation. A further outstanding characteristic of the composition lies in the fact that these beneficial properties are obtained without adverse effect from other conventional additives commonly employed in lubricant compositions. Still another advantage particular alloy bearings such as the silver metal-containing bearings more and more commonly found in marine and railroad diesel engines.

In a more specific and preferred embodiment the pres ent invention is concerned with a lubricant composition comprising an oil of lubricating viscosity in combination with a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use, and a minor portion, sufiicient to inhibit corrosion, of p-Xylylenediamine, said minor portion of lubricating oil detergent additive being sufiicient to suspend said p-xylylenediamine in the oil of lubricating viscosity.

The lubricating oil detergent additive of the composition is a well known type of additive generally used in lubricant compositions. The term, as employed here in its This type of lubricating oil detergent additive, for present purposes,"may be conveniently described as a macromolecular copolymer characterized by oil solubilizing monomer groups and polar-type monomer groups which apparently provide the detergent effect. The oil solubilizing monomer which is well known in the field of polymeric lubricating oil viscosity index improvers may be an olefin such as hexadecene-l or p-octyl styrene; an ester such as allyl stearate or lauryl methacrylate; an ether such as vinyl n-butyl ether; or a ketone such as methallyl isobutyl ketone. The polar type'monomer groupmay be an unsaturated monocarboxylic'acid suchas methacrylic .acid, amides and esters thereof such as'n-lauryl acrylamide and pentaerythritol monomethacrylate, unsaturated dicarboxylic acids such as maleic acid and amides and esters thereof-such as the half-amides, half-esters, diamides and diesters as illustrated by the N,N-di-tert.butyl monoamide of maleicacid, monopentaerythritol ester of maleic acid and similar diamides and diesters.

Other oil-soluble dispersants may be included in the lubricant compositions either in addition to or in lieu of the metallic and nonmetallic' lubricating oil detergent additives described above. Such dispersants are illustrated by the phosphatides such as animal lecithin and the'partial or complete estersiof long-chain carboxylic acids with polyhydric alcohols such as pentaerythritol mono-oleate and glycerol sorbitan laurate. These materials, like the other dispersants or lubricating oil detergent additives mentioned previously, also serve to maintain the pxylylenediamine of the present compositions in stable suspension. Thus, the p-xylylenediamine is circulated freely in the lubricating oil system wherever corrodible metal surfaces are encountered to effectively inhibit corrosion and promote improved lubrication of rubbing sur faces.

The p-xylylenediarnine is a known material. It may be conveniently derived by converting terephthalic acid to the t'erephthaladinitrile which is then hydrogenated to give the p-xylylenediamine. In view of the remarkably improved corrosion-inhibited lubricant compositions obtained when it is combined with oils of lubricating viscosty, .however, a brief review of its more important characteristics may be appropriate here. structurally, the p-xylylenediamine is unique 'in that the two amine groupsare attached to methylene groups which are separated by the benzene ring as illustrated by the following formula:

nnvcmOor-nnm This particular amine, it will-be noted, is unlike other amines in that the two amine groups are located where they will be able to function most effectively without affecting each other. Other diamines of both' aliphatic and aromatic types generally lack the structural characteristics of the p-xylylenediamine and this can lead to undesirable variations in their effectiveness under the many different conditions of operation encountered with lubricant compositions.

The compositions of this invention containing the pxylylenediamine, as described above, are surprisingly more effective in the inhibition of corrosion of metal surfaces such as alloy metal bearings and the like than similar compositions containing their homologue, p-phenylenediamine. Still more unexpected is the fact'that the pxylylene-diamine is a much better corrosion inhibitorthan its isomer, m-xylylenediamine; So far as is'known, it has never been suggested heretofore that either of these xylylenediamines might be effective in lubricant compositions as corrosion inhibitors, let alone that p-xylylenediamine would be far superior to its isomer, m-xylylenedi amine in such a capacity. 1

In accordance with a preferred embodiment ofthe invention, as already described, a' lubricating oil detergent additive is present in a minor amount, suflicient'to suspend the p-xylylenediamine in the oil of lubricating viscosit'y. Amounts up to 20% by weight of the lubricant composition are generally suitable for this purpose, although concentrates for use in blending operations to prepare the lubricant compositions of the invention may contain up to 50% by weight or more of the detergent. For present purposes, very superior lubricant compositions are obtained with from 0.1 to 10% by weight of the detergent.

The p-xylylenediamine is present in the lubricant composition in a minor portion, sufficient to inhibit corrosion, as stated above. Generally,,amounts up to about 1.0% by weight of the lubricant composition are very satisfactory. Larger amounts,'up to 10% or more, may be used in the preparation of concentrates. For present purposes the preferred lubricant compositions contain from about 0.001 to 0.5 %by weight. Such'compositions are unusually stable and provide remarkably efiective corrosion inhibition for extended periods.

Any of thewell known types of oils of lubricating viscosity are suitable base oils for the compositions of the invention. In normal usage these oils are corrosive to metal surfaces. They include hydrocarbon or mineral lubricating oils of naphthenic, paraflinic, and mixed naphthenic and paraffinic types. They may be refined by any of the conventional methods such as solvent refining andacidrefining. Synthetic hydrocarbon oils of the alkylene polymer type or those derived from coal and shale may also be employed. Alkylene oxide polymers and their derivatives such as the propylene oxide polymers and their ethyl esters and acetyl derivatives in which the terminal hydroxyl groups have been modified are also suitable. Synthetic oils of the dicarboxylic acid ester type including dibutyl adipate, di-2-ethylhexyl sebacate, di-nhexyl fumarate polymer, di-lauryl acylate, and the like may be used. Alkyl benzene types of synthetic oils such as tetradecyl benzene, etc., are also included. Liquid esters of acids of phosphorus including tricresyl phos phate, diethyl esters of decane phosphonic acid and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxy-' and polyaryloxy siloxanes such as polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils such as tetraalkyland tetraaryl silicates of the tetra-Z-ethylhexyl silicate and tetra-p-tert.-butylphenyl silicate types.

As already mentioned, the corrosion inhibiting compositions of this invention are outstanding in thattheyare unusually effective in the form of compounded lubricating oils containing conventional additives such as oxidation inhibitors, detergents or dispersants, sludge inhibitors, pour depressants, VI improvers, antifoaming agents, rust inhibitors, oiliness or film strengthening agents, wear inhibitors, dyes and the like. A great many of these compounded 'oils are generally corrosive to metal surfaces andalloy metal bearings in particular, and it is an ex-' ceptional attribute of the present compositions whereby corrosion inhibited compounded lubricating oils are provided. 'A further very desirable feature of the compositions according to. the invention is 'the fact that the corrosi-on inhibition is obtained Without any noticeable adverse eflect'on the other additives, thus permitting more efficient "all around lubrication of internal combustion engines and other types of machines where unusually severe conditions of service are 'more and more commonly encountered. i V

Minerallubricating oils are preferred in the compounded lubricating oil compositions of the invention since such oils are generally compounded for internal combustion' engine use'are unusually corrosive to metal surfaces and are thus most greatly benefited by the addition of p-xylylenediamine. I e

.The following examples are submitted as addition illustrations of the invention. These examples show the preparation of the various lubricant compositions and the evaluation of their elfectiveness as corrosion inhibitors. The proportions given in these examples, unless otherwise specified, are on a weight basis and include both percent and millimoles per kilogram (mM/kg.) of the various additives.

EXAMPLE I Approximately 350 parts of a mineral oil concentrate consisting of a solvent refined SAE 30 mineral lubricating oil base, mM/kg. of basic calcium petroleum sulfonate analyzing 1.67% calcium and 36 mM/kg. of a sulfurized basic calcium alkyl phenate analyzing 3.10% calcium was charged to a reaction vessel equipped with stirring and heating means. The contents were heated up to 160 P. 0.175 part of p-xylylendiamine was added to the reaction vessel and the contents were stirred at 200 F. for about 10 minutes. The resulting composition was a solvent refined SAE 30 mineral lubricating oil containing 10 mM/kg. of basic calcium petroleum sulfonate analyzing 1.67% calcium, 36 mM/kg. sulfurized basic calcium alkyl phenate analyzing 4.4% calcium and 0.05% p-xylylenediamine.

By the same general procedure as outlines in the above example additional corrosion inhibited lubricant compositions were prepared in illustration of the invention. They contained both mineral oils and a variety of synthetic oils used either alone with the p-Xylylenediamine or in combination with conventional lubricating oil additives to illustrate the overall efliectiveness of the compositions in accordance with this invention. The compositions and their eifectiveness in standard lubricating oil tests for determining corrosion inhibition are listed in the following table. This table shows specific results obtained by the Copper-Lead Strip Corrosion Test.

In the Copper-Lead Strip Corrosion Test, a polished copper-lead strip is Weighed and immersed in 300 m1. of test oil contained in a 400 ml., lipless Berzelius beaker. The test oil is maintained at 340 F. under a pressure of 1 atmosphere of air and stirred with the mechanical stirrer at 1000 R. P. M. After 2 hours, a synthetic naphthenate catalyst is added to provide the following catalytic metals:

Percent by weight Iron 0008 Lead 0.004 Copper 0.002 Manganese 0.0005 Chromium 0.004

The test is continued for 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and Weighed to determine the net weight loss.

The lubricating oil compositions in the tests include a variety of base oils. Mineral oil (A) is an acid refined White mineral oil. Synthetic oil (B) is a poly-1,2-propylene glycol phenyl methyl diether having a molecular weight of 1200. Synthetic oil (C) is a di-Z-ethylhexyl sebacate. Compounded oil (D) is a solvent refined SAE .0 mineral lubricating oil having a viscosity index of 60 and containing 10 mM/kg. of basic calcium petroleum sulfonate and 20 mM/kg. of sulfurized basic calcium cetyl phenate. Compounded oil (E) is the same mineral lubricating oil but contains only 10 mM/kg. basic calcium petroleum sulfonate. Compounded oil (F) is the same inineral lubricating oil but contains 14 mM/ kg. lead cetyl phenate. Compounded oil (G) is an acid refined white mineral oil containing 10% by weight of a copolymeric detergent which is the copolymer of lauryl methacrylate with the diethylaminoethyl ester of acrylic acd sold by DuPont as Lubricating Oil Additive No. 56S. Compounded oil (H) is the same oil but contains 20 mM/kg. sulfurized basic calcium cetyl phenate.

Illustrative test results are shown in the following table. Concentrations of the p-xylylenediamine employed are given in percent by weight of the composition.

' synthetic lubricating oils 6 Table COPPER-LEAD STRIP CORROSION TEST Copper-Lead Additive and 011 Strip Weight Loss (Mgn) NoneMineral 011 (A) 66. 2 0.15% p-xylylenediamine in m or 0. 0 N one-Synthetie oil (B) 4. 4 0.15% p-xylylenediamine in synthetic oil (B). 0. 0

one-Synthetic oil (0) 46.8 0.15% p-xylylenediamine in synthetic oil (0).". 11. 6 N one00mpounded oil (D) 250300 0.25% o-phenylenediamine in compounded 011 (D) 260. 9 0.5% o-phenylenediamine in compounded oil (D) 216. 2 0.25% m-phenylenediamine in compounded oil (D) 82. 6 0.5% m-phenylenediamine in compounded oil (D) 82. 2 0.25% p-phenylenediamine in compounded oil (D) 69. 9 0.5% p-phenylenediamine in compounded oil (D) 67. 9 0.25% m-xylylenediamine in compounded 011 (D)... 108. 9 0.25% p-xylylenediamiue in compounded 011 (D) 3. 3 0.10% p-xylylenediamine in compounded oil (D) 13.2 N one-Compounded oil (E) 272. 4 0.15% p-xylylenediamiue in compounded oil (E 17. 5 N oneC0mpounded oil (F) 270. 4 0.15% p-xylylenediamine in compounded 011 (F) 74. 2 N one-Compounded oil (G) 158. 6 0.15% p-xylylenediomine in compounded oil (G). 0.0 None-Compounded oil (H) 172. 6 0.15% p-xylylenediamine in compounded oil (H) 18. 9

The above test data show that all of the various mineral oils and synthetic oils alone or in combination with conventional lubricating oil additives which are normally corrosive to metal surfaces are all benefited with the addition of p-xylylenediamine corrosion inhibitor in accordance with the invention. The effectiveness of oils of lubricating viscosity in general which are normally corrosive to metal surfaces in the corrosion inhibited compositions of the invention is illustrated by a representative group consisting of mineral lubricating oils, alkylene oxide polymer and dicarboxylic acid diester synthetic lubricating oils. In one particular combination, that employing compounded oil (D), the above test data show that the reference oil containing heavy duty lubricating oil detergent additives and stabilizers, when used alone, gives a copper-lead strip loss of over 250 mg. By way of distinction, compositions in accordance with this invention employing the same base oil with as little as 0.10% p-xylylenediamine, for example, give a very low corrosion loss of only 13.2 mg. This outstanding effectiveness of the present compositions containing pxylylenediamine is remarkable, because the isomers and adjacent homologues of p-xylylenediarnine (for example, m-xylylenediamine and p-phenylenediamine, respectively) in similar compositions are largely inefiective and, therefore, unsatisfactory as corrosion inhibitors.

Although the compositions of the invention have been described above primarily as internal combustion engine lubricants they are also suitable for other applications. Such applications include their use as gear lubricants, ice machine oils, instrument oils, constituent oils for grease manufacture, turbine oils and the like.

This application is a continuation-in-part of Warren Lowe patent application Serial No. 476,088, filed December 17, 1954, entitled Corrosion Inhibited Lubricant Composition, now abandoned.

I claim:

1. A lubricating composition comprising a major portion of an oil of lubricating viscosity corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion of p-xylylenediamine.

2. A lubricating composition comprising a major portion of a mineral lubricating oil corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion, of p-xylylenediamine.

3. A lubricating composition comprising a major portion of an oil of lubricating viscosity in combination with a minor portion of a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use and a minor portion, sufiicient to inhibit corrosion, of p-xylylenediamine, said minor portion of lubri- -4.- A lubricating composition comprising a major per-- tion ofamineral lubricating oil in combination with a minor portion of a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use. and a minor portion, sufficient to inhibit corrosion,

ofp-Xylylenedianiinef,1said minorpor'tion of lubricating oil detergent additive being sufficient-to suspend said p xylylenediamine'in' the mineral lubricating oil.

5. A lubricating composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of' an alkaline earth'metal petroleum sulfonate, said combination being corrosive to metal surfaces in'normal use and a minor portion, sufiicient to inhibit corrosion, of pxylylenediamine, said minor portion of alkaline earth metal petroleum sulfonate being sufficient to suspend said p-xylylenediaminetin. the mineral lubricating oil. 6. A lubricating comp'ositioncomprising a major portion of a mineral lubricating oil in combination with a minor portion of an.alkaline earth metal petroleum sulfonate and an alkaline earth metal alkyl phenate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion of p-xylylenediamine, said minor portion of alkaline earth metal petroleum sulfonate and alkaline earth metal t v n V 7 alkyl phenate: being suiiicient to suspend saidp-Xylylenediamine in themi'neral lubricating oil.

Atlubi'icatirig compos tion of amineral lubricating oil in'combination with a minor portion of a calcium petroleum sulfonate, said com bination being corrosive'to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of pxylylenediamineg said minor portion of calcium petroleum sulfonate being sufiicient to suspend said p-xylylenediamine in the mineral lubricating oil.

8. A lubricating composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of acalcium petroleum sulfonate and a calcium alkyl phenate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion of p-Xylylenediamine, said minor portion of calcium petroleum sulfonate and calcium alkyl phenate being sufiicient to suspend said p-xylylenediamine in the mineral lubricating oil.

References Cited in the file of this patent UNITED STATES PATENTS ition compriisin'gla majorer: 

1. A LUBRICATING COMPRISING A MAJOR PORTION OF AN OIL OF LUBRICATING VISCOSITY CORROSIVE TO METAL SURFACES IN NORMAL USE AND A MINOR PORTION, SUFFICIENT TO INHIBIT CORROSION OF P-XYLYLENEDIAMINE. 